// SurfZPlane.h

#ifndef SurfZPlane_H
#define SurfZPlane_H

// Defines the pure suface correponding to a plane perpendicular to
// the z-axis.
//
// The corresponding track parameters are:
// z (cm) is fixed 
// 0 - x (cm)
// 1 - y (cm)
// 2 - dx/dz 
// 3 - dy/dz 
// 4 - q/p   p is momentum of a track, q is its charge
//
// This class serves as a base class for bounded cylinders.
//
// The forward direction for the surface is +z.

#include "trfbase/Surface.h"

namespace trf {

class VTrack;
class CrossStat;

class SurfZPlane : public Surface {

public:  

// enums identifying surface parameters
  enum {ZPOS = 0};

  // track parameter indices
  enum { IX=0, IY=1, IDXDZ=2, IDYDZ=3, IQP=4 };
 
public:

  // Return the type name.
  static TypeName get_type_name() { return "SurfZPlane"; }

  // Return the creator.
  static ObjCreator get_creator();

  // Return the type.
  static Type get_static_type() { return get_creator(); }

protected:  // attributes

  double _z;

protected:

  // Output stream operator.
  // used by operator<<.
  virtual void ostr(std::ostream& stream) const;
  void raw_ostr(std::ostream& stream) const;

  // Return true if two surfaces have the same pure surface.
  // Argument may be safely downcast.
  bool safe_pure_equal(const Surface& srf) const;

  // Return true if this surface and the argument are in order.
  // See Surface::pure_less_than() for more information.
  // Argument may be safely downcast.
  bool safe_pure_less_than(const Surface& srf) const ;

public:

  // constructor
  SurfZPlane(double z);

  // destructor
  virtual ~SurfZPlane();

  // pure type
  Type get_pure_type() const { return  get_static_type(); };

  // Write the object data.
  ObjData write_data() const;

  // Virtual constructor.
  SurfZPlane* new_pure_surface() const;
  
  // Find crossing status for a track.
  CrossStat pure_status(const VTrack& trv) const;

  // Return the surface parameter.
  double get_parameter(int i) const;

  // Return the z position.
  double get_z() const { return _z; };

  // Return the difference between two track vectors.
  TrackVector vec_diff(const TrackVector& vec1, 
                       const TrackVector& vec2) const;

  // Return the space point for a track vector.
  SpacePoint space_point(const TrackVector& vec) const;

  // Return the space vector for a track vector.
  SpacePath space_vector(const TrackVector& vec, 
                         TrackSurfaceDirection dir) const;

};

}  // end namespace trf

#endif